Semiconductor integrated circuit device having ground connections arranged to eliminate mutual interference between island-disposed electronic circuits

Abstract

A semiconductor integrated circuit contains a plurality of electronic circuit portions formed thereon, each of which includes an earth wiring. Mutual interference between the circuit portions is reduced by connecting the earth wirings to a common earth electrode, and connecting only a part of the earth wirings to an earth point of the semiconductor substrate.

What is claimed is: 
     
       1. A semiconductor integrated circuit device, comprising; at least two electronic circuit portions formed in a common semiconductor substrate, at least two island regions wherein said electronic circuit portions are respectively formed, a plurality of separation regions respectively formed between adjacent island regions and being electrically contiguous with said substrate, earth electrodes for said substrate being disposed on ones of said separation regions, substrate earth wirings having first and second ends and being connected at first ends to said earth electrodes, a plurality of circuit earth wirings having first and second ends and being connected at first ends to said electronic circuit portions, and a common earth electrode formed on said semiconductor integrated circuit device and directly connected to the second ends of said substrate earth wirings and to a substantial majority of the second ends of said circuit earth wirings, a substantial minority of said second ends of said circuit earth wirings being electrically connected to adjacent ones of said substrate earth wirings, wherein the number of said substrate earth wirings connected to said circuit earth wirings is limited in a manner so as to reduce mutual interference between said circuit portions by reducing the effect of intrinsic parasitic impedances of the circuit device. 
     
     
       2. A semiconductor integrated circuit device as claimed in claim 1; wherein said semiconductor substrate is formed of a first semiconductor layer of one conductivity type, a second semiconductor layer of the opposite conductivity type being formed on said first semiconductor layer, said second semiconductor layer being divided into said island regions by said separation regions, said separation regions being of said one conductivity type and extending downwardly from the surface of said substrate. 
     
     
       3. A semiconductor integrated circuit device as claimed in claim 2, wherein said second semiconductor layers are epitaxially grown layers and said separation regions are impurity diffusion layers. 
     
     
       4. A semiconductor integrated circuit device, comprising; a semiconductor substrate of a first conductivity type,   first and second island regions of a second conductivity type formed in one main surface of said substrate, said first and second island regions being separated from one another by a separation region of said first conductivity type,   a common earth electrode formed on said one main surface of said substrate,   a substrate earth electrode electrically connected to said separation region and disposed adjacent to said first island region, and said substrate earth electrode being electrically connected through a substrate earth wiring to said common earth electrode,   a first electronic circuit portion having a first electrode formed on said first island region, a circuit earth wiring for electrically connecting said first electrode to said common earth electrode, said circuit earth wiring being joined to said substrate earth wiring at a location of said substrate earth wiring between said first electrode and said common earth electrode,   a second electronic circuit portion having a second electrode formed on said second island region, and a circuit earth wiring for directly connecting said second electrode to only said common earth electrode.   
     
     
       5. A semiconductor integrated circuit device as claimed in claim 1; only one of said plurality of said circuit earth wirings being connected to said substrate earth electrode. 
     
     
       6. A semiconductor integrated circuit device as claimed in claim 1, wherein a first of said electronic circuit portions is grounded via a first one of said circuit earth wirings, said first circuit earth wiring being electrically connected to one of said substrate earth electrodes via a substrate earth wiring, and wherein further ones of said electronic circuit portions adjacent to said first electronic circuit portion are grounded via further ones of said circuit earth wirings, said further ones of said circuit earth wirings being electrically disconnected from said one substrate earth electrode, and being electrically connected to said common earth electrode. 
     
     
       7. A semiconductor integrated circuit device, comprising; at least two electronic circuit portions (7, 8) formed in a common semiconductor substrate (1), at least two island regions (5, 6) wherein said electronic circuit portions are respectively formed, a plurality of separation regions (2, 3, 4) respectively formed between adjacent island regions and being electrically contiguous with said substrate, earth electrodes (9) for said substrate disposed on ones of said separation regions, substrate earth wiring (00) having first and second ends and being connected at first ends to said earth electrodes, a plurality of circuit earth wirings (500) having first and second ends and being connected at first ends to said electronic circuit portions, a common earth electrode formed on said semiconductor integrated circuit device and directly connected to the second ends of said substrate earth wirings and to a substantial majority of the second ends of said circuit earth wirings, a substantial minority of the second ends of said second earth wirings being electrically connected to adjacent ones of said substrate earth wirings, wherein a first of said electronic circuit portions is grounded via a first one of said circuit earth wirings, said first circuit earth wiring being electrically connected to one of said substrate earth electrodes via a substrate earth wiring, and wherein said second and further ones of said electronic circuit portions located directly adjacent said first electronic circuit portion are grounded via further ones of said circuit earth wirings, said further ones of said circuit earth wirings being electrically disconnected from said one substrate earth electrode, and being directly electrically connected to said common earth electrode.